def get_grade(score):
    if score <0 or score > 100:
        return "Invalid score"
    elif score >= 90:
        return "A"
    elif score >= 80:
        return "B"
    elif score >= 70:
        return "C"
    elif score >= 60:
        return "D"

Your_score = int(input("请输入你的成绩："))
print(get_grade(Your_score))
